11,567 research outputs found
Critical line of the deconfinement phase transition
Phase diagram of strongly interacting matter is discussed within the exactly
solvable statistical model of the quark-gluon bags. The model predicts two
phases of matter: the hadron gas at a low temperature T and baryonic chemical
potential muB, and the quark-gluon gas at a high T and/or muB. The nature of
the phase transition depends on a form of the bag mass-volume spectrum (its
pre-exponential factor), which is expected to change with the muB/T ratio. It
is therefore likely that the line of the 1st} order transition at a high muB/T
ratio is followed by the line of the 2nd order phase transition at an
intermediate muB/T, and then by the lines of "higher order transitions" at a
low muB/T.Comment: 13 pages, 6 figure
X-ray emission from the PSR B1259--63 system near apastron
The PSR B1259--63 system contains a 47 ms radio pulsar in a highly eccentric
binary with a Be-star companion. Strongly time variable X-ray emission was
reported from this system as the pulsar was near apastron in 1992-early 1993.
The variability was primarily deduced from an apparent non-detection of the
\psr system during a first pre-apastron \ros observation in February~1992. We
have re-analyzed the \ros observations of the \psr system. Contrary to the
results of a previous analysis, we find that the \psr system was detected by
\ros during the first off-axis February~1992 observation. The intensity of the
soft X-ray emission of the \psr system before and after the 1992 apastron
appears to vary at most by a factor . Our results sensibly constrain
theoretical models of X-ray emission from the \psr system.Comment: LATEX, Accepted for publ. in ApJ
Exit polling and racial bloc voting: Combining individual-level and RC ecological data
Despite its shortcomings, cross-level or ecological inference remains a
necessary part of some areas of quantitative inference, including in United
States voting rights litigation. Ecological inference suffers from a lack of
identification that, most agree, is best addressed by incorporating
individual-level data into the model. In this paper we test the limits of such
an incorporation by attempting it in the context of drawing inferences about
racial voting patterns using a combination of an exit poll and precinct-level
ecological data; accurate information about racial voting patterns is needed to
assess triggers in voting rights laws that can determine the composition of
United States legislative bodies. Specifically, we extend and study a hybrid
model that addresses two-way tables of arbitrary dimension. We apply the hybrid
model to an exit poll we administered in the City of Boston in 2008. Using the
resulting data as well as simulation, we compare the performance of a pure
ecological estimator, pure survey estimators using various sampling schemes and
our hybrid. We conclude that the hybrid estimator offers substantial benefits
by enabling substantive inferences about voting patterns not practicably
available without its use.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS353 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Thermalization of Hadrons via Hagedorn States
Hagedorn states are characterized by being very massive hadron-like
resonances and by not being limited to quantum numbers of known hadrons. To
generate such a zoo of different Hagedorn states, a covariantly formulated
bootstrap equation is solved by ensuring energy conservation and conservation
of baryon number , strangeness and electric charge . The numerical
solution of this equation provides Hagedorn spectra, which enable to obtain the
decay width for Hagedorn states needed in cascading decay simulations. A single
(heavy) Hagedorn state cascades by various two-body decay channels subsequently
into final stable hadrons. All final hadronic observables like masses, spectral
functions and decay branching ratios for hadronic feed down are taken from the
hadronic transport model UrQMD. Strikingly, the final energy spectra of
resulting hadrons are exponential showing a thermal-like distribution with the
characteristic Hagedorn temperature
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